Application of density functional theory to calculation of in-crystal anionic polarizability

Density functional calculations of polarizability and its derivative with lattice parameter are reported for F− in LiF and O2− in MgO, using embedded cluster techniques. With typical functionals (LDA, BLYP, B3LYP) the polarizability is physically realistic only when the anion density is fully compressed in the crystal. Near equilibrium, polarizability is overestimated by 10–20%: it grows uncontrollably with lattice expansion. Overlap compression of the in-crystal anion renders it insensitive to the asymptotic exchange-correlation potential, so that the performance of density functional theory near equilibrium becomes comparable to that for neutral molecules. The hybrid B3LYP functional gives the best results.